Art of producing colored photographs



diluted glycerine.

UNITED STATES PATENT OFFICE.

JAMES W. MCDONOUGH, CHICAGO, ILLINOIS.

ART OF PRODUCING COLORED PHOTOGRAPHS.

SPECIFICATION forming part of Letters Patent No. 471,187, dated March22, 1892.

Application filed October 5,1891- Serial No. 407,787. (No specimens.)

To all whom it may concern:

Be it known that 1, JAMES W. MCDONOUGH, a citizen of the United States,residing at Ohicago, Illinois, have invented a certain new andusefullmprovement in the Art of Producing Colored Photographs, of whichthe following is a specification.

I take a support of plain glass, celluloid, paper, or other suitablesubstance, upon the surface of which is a sensitive photographiccoating, preferably forming what is known as an orthrochromaticdry-plate. This may be rendered tacky by immersion in water or Ifpreferred, however, the plate may be used before it becomes quite dry inthe course of its manufacture. I dust the plate,.either while it issomewhat moist in the course of its manufacture or after it has becometacky, as above explained, witha mixture of colors composed of fine orpowdered particles containing the colors desired. I thus obtain acolored surface composed of particles lying side by side, which have theproperties of stippled colors instead of the properties of a truemixture of pigments. In order to get these colored particles, I usecolored powdered glass, transparent pigments, gelatine, rosin, shellac,or similar substances stained by aniline dyes, &c. In the preparation ofthe colors by means of shellac I take a sufficient quantity of cleanwhite shellac dissolved in alcohol, to which I add aniline colors-say,for one lot red and yellow colors-in such proportions that the resultwill be a red, which when Viewed by transmitted light in layers will cutoff or absorb as much green, blue, violet, and yellow as possible, orwhich, in other words, will transmit as far as possible a pure red.Another lot is colored with as pure a green as may be formed by mixturesadding yellow to absorb blue. Another lot is colored blue. As themixture of colors formed in this way by red and green does not form abright yellow, I may use in addition another lot colored as near theyellow of the spectrum as possible. These lots after being thus coloredare allowed to dry, forming colored masses, which are then reduced topowder by grinding, sifting, &c. If now proper proportions of red andgreen are mixed, a nearly black or gray mass will be formed,

and if proper proportions of red, green, yellow, and blue are mixed amass be will formed that is nearly black or gray; but if this samemixture is dusted or finely spread upon the prepared sensitive surfaceit will reflect or transmit a mixture of all these colors, which will bewhite in proportion to the purity of color, cleanliness of mixture, andquantity of light transmitted or reflected. The glycerine may be washedout, so that only the colored particles in the mass in which they arearranged remain. When viewed under the microscope, the white surface isseen to be composed of a multitude of different-colored particles lyingside by side and separated by small distances. This surface may beflowed with a thin coat of gelatine, which will penetrate the spacesbetween the colored particles, or the ground and colored particles maybe coated with gelatine'before applying them to the tacky surface bymixing them with a small quantity of dissolved gelatine and regrindingthem, according as a mat or smooth surface is .required.

The process of producing the effect called color, above described, is byabsorption of light; but inasmuch as color-effects may also be producedby refraction, dispersion, or diffraction of light 'I do not mean tolimit myself to absorption only as the means of producing them.

The photographic plate thus obtained consisting of colored particlesapplied to its sensitive surface may be exposed to the action of thelight from the object to be photographed through a camera in such mannerthat this light will pass through the colored particles and affect thesensitive film, thus producing a latent image of the object. The platemay then be developed by the use of the so-calledalkaline-pyrodeveloper," so that the colored particles will adhere tothe surface which is penetrated by the same colored light as theparticles themselves, because gelatine is rendered insoluble inproximity to the silver particles in the sensitive compound where actedupon by light. Thus particles which do not allow the passage of coloredrays on account of absorption may be washed off, because as to suchparticles the gelatine remains soluble. Thus blue rays will cause IOOblue particles to remain as an image, white light all the coloredparticles in that space acted upon by white light, and all will beremoved where black occurs, which does not act upon the photographicfilm. After the development the picture may be treated with thiosulphateof soda to remove the sensitive compound not acted on by the light anddeveloper. By thus developing the platea picture is produced composed ofthe particles of silver and the colored particles remaining on the plateafter the development. This picture may be used as a negative or backedwith a black or other colored s'u rface, as in an ambrotype. The coloredimage is formed by the reflection of, light from the particles orthrough the particles from the silver image or by the transmission oflight through them when not cut off by the image. The use of theorthrochromatic sensitive plates and colored screens before the camerafor the purpose of sifting light and regulating the action of differentcolors upon the film is too well known to require explanation. I willmerely add that the particles are dusted, spread, or placed upon theplate in such proportions as to produce a white or transparent surface.

'upon by light, substantially as described.

3. A plate for photographic purposes, having a sensitive surface towhich is applied a layer of different-colored particles lying side byside and in such proportions as to produce a white or light-coloredtransparent surface, substantially as described.

JAMES W. MODONOUGH.

\Vit-nesses:

SAMUEL E. HIBBEN, ANNIE (J. OOURTENAY.

